List of free performance stuff for developerππ½
If you're looking for all programming tools around performance (not just free). Check this page List of performance Programming Tools

Autocompress: Image optimization for Bitbucket
Optimizes the images in your Bitbucket repositories
Tag: image, optimization, compression, static assets, serverless, performance, asset, hosting-static, storage
Unlimited for public repos. 14-day trial for private repos (enough to compress all your images)

DebugBear Speed Test
Measure the speed and Core Web Vitals of your website. Find out how to make your website load faster and rank well in Google.
Tag: analytics, performance
Free website test